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  <title>计算数组中的单元数目，或对象中的属性个数</title>
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  <div id="layout-content"><div id="function.count" class="refentry">
   <div class="refnamediv">
    <h1 class="refname">count</h1>
    <p class="verinfo">(PHP 4, PHP 5, PHP 7)</p><p class="refpurpose"><span class="refname">count</span> &mdash; <span class="dc-title">计算数组中的单元数目，或对象中的属性个数</span></p>

   </div>
 <div class="refsect1 description" id="refsect1-function.count-description">
  <h3 class="title">说明</h3>
  <div class="methodsynopsis dc-description">
   <span class="methodname"><strong>count</strong></span>
    ( <span class="methodparam"><span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span> <code class="parameter">$array_or_countable</code></span>
   [, <span class="methodparam"><span class="type">int</span> <code class="parameter">$mode</code><span class="initializer"> = COUNT_NORMAL</span></span>
  ] ) : <span class="type">int</span></div>

  <p class="para rdfs-comment">
   统计出数组里的所有元素的数量，或者对象里的东西。
  </p>
    <p class="para">
     对于对象，如果安装了 <a href="ref.spl.html" class="link">SPL</a>，可以通过实现
     <em>Countable</em> 接口对 <span class="function"><strong>count()</strong></span>挂钩（hook）
     。该接口只有一个方法
     <span class="methodname"><a href="countable.count.html" class="methodname">Countable::count()</a></span>，此方法为 <span class="function"><strong>count()</strong></span>
     函数返回值。
    </p>
    <p class="para">
     关于 PHP 中如何实现和使用数组可以参考手册中<a href="language.types.array.html" class="link">数组</a>章节中的详细描述。
  </p>
 </div>

    <div class="refsect1 parameters" id="refsect1-function.count-parameters">
  <h3 class="title">参数</h3>
  <p class="para">
   <dl>

    
     <dt>
<code class="parameter">array_or_countable</code></dt>

     <dd>

      <p class="para">
       数组或者 <a href="class.countable.html" class="classname">Countable</a>  对象。
      </p>
     </dd>

    
    
     <dt>
<code class="parameter">mode</code></dt>

     <dd>

      <p class="para">
       如果可选的 <code class="parameter">mode</code> 参数设为
     <strong><code>COUNT_RECURSIVE</code></strong>（或 1），<span class="function"><strong>count()</strong></span>
     将递归地对数组计数。对计算多维数组的所有单元尤其有用。
      </p>
      <div class="caution"><strong class="caution">Caution</strong>
       <p class="para">
        <span class="function"><strong>count()</strong></span> 能检测递归来避免无限循环，但每次出现时会产生 <strong><code>E_WARNING</code></strong> 错误
        （如果 array 不止一次包含了自身）并返回大于预期的统计数字。
       </p>
      </div>
     </dd>

    
   </dl>

  </p>
 </div>

 <div class="refsect1 returnvalues" id="refsect1-function.count-returnvalues">
  <h3 class="title">返回值</h3>
  <p class="para">
   返回 <code class="parameter">array_or_countable</code> 中的单元数目。
   
   如果参数既不是数组，也不是实现
     <em>Countable</em> 接口的对象，将返回
     <em>1</em>。
   有个例外：如果
     <code class="parameter">array_or_countable</code> 是 <strong><code>NULL</code></strong> 则结果是 <em>0</em>。
  </p>
 </div>

 <div class="refsect1 examples" id="refsect1-function.count-examples">
  <h3 class="title">范例</h3>
  <p class="para">
   <div class="example" id="example-6090">
    <p><strong>Example #1 <span class="function"><strong>count()</strong></span> 例子</strong></p>
    <div class="example-contents">
<div class="phpcode"><pre><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br />$a</span><span style="color: #007700">[</span><span style="color: #0000BB">0</span><span style="color: #007700">]&nbsp;=&nbsp;</span><span style="color: #0000BB">1</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$a</span><span style="color: #007700">[</span><span style="color: #0000BB">1</span><span style="color: #007700">]&nbsp;=&nbsp;</span><span style="color: #0000BB">3</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$a</span><span style="color: #007700">[</span><span style="color: #0000BB">2</span><span style="color: #007700">]&nbsp;=&nbsp;</span><span style="color: #0000BB">5</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">count</span><span style="color: #007700">(</span><span style="color: #0000BB">$a</span><span style="color: #007700">));<br /><br /></span><span style="color: #0000BB">$b</span><span style="color: #007700">[</span><span style="color: #0000BB">0</span><span style="color: #007700">]&nbsp;&nbsp;=&nbsp;</span><span style="color: #0000BB">7</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$b</span><span style="color: #007700">[</span><span style="color: #0000BB">5</span><span style="color: #007700">]&nbsp;&nbsp;=&nbsp;</span><span style="color: #0000BB">9</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$b</span><span style="color: #007700">[</span><span style="color: #0000BB">10</span><span style="color: #007700">]&nbsp;=&nbsp;</span><span style="color: #0000BB">11</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">count</span><span style="color: #007700">(</span><span style="color: #0000BB">$b</span><span style="color: #007700">));<br /><br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">count</span><span style="color: #007700">(</span><span style="color: #0000BB">null</span><span style="color: #007700">));<br /><br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">count</span><span style="color: #007700">(</span><span style="color: #0000BB">false</span><span style="color: #007700">));<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</pre></div>
    </div>

    <div class="example-contents"><p>以上例程会输出：</p></div>
    <div class="example-contents screen">
<div class="cdata"><pre>
int(3)
int(3)

Warning: count(): Parameter must be an array or an object that implements Countable in … on line 12 // PHP 7.2 起
int(0)

Warning: count(): Parameter must be an array or an object that implements Countable in … on line 14 // PHP 7.2 起
int(1)
</pre></div>
    </div>
   </div>
  </p>
  <p class="para">
   <div class="example" id="example-6091">
    <p><strong>Example #2 递归 <span class="function"><strong>count()</strong></span> 例子</strong></p>
    <div class="example-contents">
<div class="phpcode"><pre><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br />$food&nbsp;</span><span style="color: #007700">=&nbsp;array(</span><span style="color: #DD0000">'fruits'&nbsp;</span><span style="color: #007700">=&gt;&nbsp;array(</span><span style="color: #DD0000">'orange'</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">'banana'</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">'apple'</span><span style="color: #007700">),<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #DD0000">'veggie'&nbsp;</span><span style="color: #007700">=&gt;&nbsp;array(</span><span style="color: #DD0000">'carrot'</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">'collard'</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">'pea'</span><span style="color: #007700">));<br /><br /></span><span style="color: #FF8000">//&nbsp;recursive&nbsp;count<br /></span><span style="color: #007700">echo&nbsp;</span><span style="color: #0000BB">count</span><span style="color: #007700">(</span><span style="color: #0000BB">$food</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">COUNT_RECURSIVE</span><span style="color: #007700">);&nbsp;</span><span style="color: #FF8000">//&nbsp;output&nbsp;8<br /><br />//&nbsp;normal&nbsp;count<br /></span><span style="color: #007700">echo&nbsp;</span><span style="color: #0000BB">count</span><span style="color: #007700">(</span><span style="color: #0000BB">$food</span><span style="color: #007700">);&nbsp;</span><span style="color: #FF8000">//&nbsp;output&nbsp;2<br /><br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</pre></div>
    </div>

   </div>
  </p>
 </div>

 <div class="refsect1 changelog" id="refsect1-function.count-changelog">
  <h3 class="title">更新日志</h3>
  <table class="doctable informaltable">
   
    <thead>
     <tr>
      <th>版本</th>
      <th>说明</th>
     </tr>

    </thead>

    <tbody class="tbody">
     <tr>
      <td>7.2.0</td>
      <td>
       当无效的 countable 类型传递给 <code class="parameter">array_or_countable</code> 参数时，<span class="function"><strong>count()</strong></span> 会产生警告。
      </td>
     </tr>

    </tbody>
   
  </table>

 </div>

  
 <div class="refsect1 seealso" id="refsect1-function.count-seealso">
  <h3 class="title">参见</h3>
  <p class="para">
   <ul class="simplelist">
    <li class="member"><span class="function"><a href="is_array.html" class="function" rel="rdfs-seeAlso">is_array()</a> - 检测变量是否是数组</span></li>
    <li class="member"><span class="function"><a href="isset.html" class="function" rel="rdfs-seeAlso">isset()</a> - 检测变量是否已设置并且非 NULL</span></li>
    <li class="member"><span class="function"><a href="empty.html" class="function" rel="rdfs-seeAlso">empty()</a> - 检查一个变量是否为空</span></li>
    <li class="member"><span class="function"><a href="strlen.html" class="function" rel="rdfs-seeAlso">strlen()</a> - 获取字符串长度</span></li>
   </ul>
  </p>
 </div>

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